Manufacture of alloys containing molybdenum



Patented Jan. 6, 1948 U'Nireo STATE-is wirsurI eprice F A'LLOYS CONTAINING rMOLYBDENUM George LesleMIIer, Hornehurch, England, as;

,signor to Murex` Limited, a corporation` of- No Y, Drawing. v Application February v2.1, 19.45, ,SeriaLNm 579,155., In GleattBtainMa'iohr8,

IOYY'Claims.

stance int'o 'the body'o`f`1the melt 44and wellbelow' the surface thereof. Thus for example the substance may' be added in the form of a briquette or enclosed in a container 'constructed o'f some material which may itself be introduced into the melt without .detriment thereto, e, g., an iron containerin the'c'ase o'f'a ferrous melt.

In the caseof ymolybdenmn :alloys it has been proposed to introduce the molybdenum in the form of roasted -molybdenite concentrates briquetted with the aid 0f a relatively small Y'proportion 'of ai carbonaceous binder which proportion may if desired be so adjusted as to provide an amount of carbon stoichiometrically"equivalent 'to 'the' oxygen content' 'of the roasted molybdenite concentrates.

The principal object' ofthe 'present invention is to provide a' simple 'arideconomical process for the manufacture fof "compact forms of a molybdenum oxide having a high degree of hardness and strength. A furtherfobject of the invention is to provide novel "compacts of a, molybdenum oxide free from carbonaceous ingredient and having a high degree of hardness and strength. Yet a further object of the invention is to provide an improved process for the manufacture of ferrous alloys containing molybdenum. Other objects will appear hereinafter.

I have now found that it is possible to form briquettes of molybdenum trioxide (M003) or other molybdenum oxide merely with the aid of an aqueous solution of ammonia, or ammonium molybdate, and that the briquettes .so produced have a surprising degree of hardness and represent a particularly convenient form in which to add the molybdenum oxide to a metallic melt since the ammonia is driven oi at a temperature much below that of the melt and no non-volatile elements other .than molybdenum and oxygen are incorporated into the bath. Ferrous melts to which molybdenum trioxide is to be added usually have a sufficient content of carbon and/or other reducing agents, such as manganese or silicon, to

reduce the oxide `and I Yhave found' that-it pler to adjust the compositionrof 'melt by adding 'molybdenum' trioxide alonethan by endeavourin'g 'to balance'tlieoxygen con-tent with a proportion of ycarbonadditionalto that*ail-readsi` present in the bath. Moreover, -I have round that a more uniform Aandspeedy reduction of'y the molybdenum trioxide takes place by mea-ns Lof reducing agents oi" "therferrous melt'AWit-h rwhich the oxideccmes into immediate and intimate' contact thanby means of lan added carbonaceou's ingredient. AIhavealso found *that the degreeeof hardness of 'the'briquettes 'necessaryto withstand rough handling can be 'achieved vvat.'relatively"lowv pressures rwith consequent 'impor-tant economies in dies 'or' moulds and 'other installation rand maintenance costs. l

According to the present invention Ipmduce' firm, coherent compact masses of a molybdenum oxide by pressing the oxide in jpowder rform 'in the presence of anadueouss'olutionof an ammonium molybdate and drying the 'pressed-product. 'The ammoniummolybdatemay be introduced, i. e.; incorporated,` rint'o admixture with 'the"m'olyb denurn oxidel either by addition in the'forr'n .off anv aqueous solution o'r by' reaction in As'itu'between themolybdenum oxide and ammonia; added .in the form o'f'an aqueous `solution Itheredf.v Pref# erably 'Iem'ploy a proportion of ammonia orammonium molybdate' (calculated asNI-l) Ylying beltween i05per cent.Y and .2 per centjloyY weighto the weight/of 'the'lmolybdenum .oxide "In igeneral the hardness and strength o`f 'thepoductincreases with the amount of ammonia added, although it will be understood that the use of an undue proportion of ammonia is uneconomic.

In that form of the invention which comprises adding aqueous ammonia to the molybdenum oxide, I prefer to employ aqueous ammonia having a concentration lying between 5 per cent. and

33 per cent. by weight. The concentration of the ammonia should be so chosen as to aiiord a suitable proportion of Water in the mix for good pressing characteristics; that is to say, independently of the proportion of ammonia (NH3) added, the proportion of Water should not be so small that the mixture is too dry to press, and should not be so large that the mixture is .too wet to press. Y

Pressures lying between 2 and 20 tons per square inch are suitable, more particularly pressures lying between 2 and 5 tons per square inch. For these pressures the proportion of water may suitably lie between .7 per cent. and 5 per cent.

by weight of the molybdenum oxide. In general an increase in pressure permits of the employment of a smaller proportion of Water. In practice I find it convenient to add about 1/2 to 1 per cent. by weight of aqueous ammonia of 0.880 specic gravity diluted with its own volume of water. It is convenient to rdistribute the aqueous medium throughout the oxide by agitating the latter in a mixing device while the solution is sprayed over the charge. formed into briquettes or other masses of convenient size and shape.

According to a further feature of the invention molybdenum is introduced as an alloying ingredient into molten metal baths containing carbon and/or other reducing agent such as manganese or silicon in solution by adding thereto an oxide of molybdenum in the form of a firm coherent pressed mass obtained in accordance with the process described and claimed herein.

The invention is illustrated but not limited by the following example.

A charge of 100 lbs. of molybdenum trioxide is introduced into a mixer and an aqueous solution of ammonia is sprayed over the charge while it is being mixed. The ammonia solution consists of 0.66 lb. of aqueous ammonia of 0.880 specific gravity diluted with 0.75 lb. of water. .The mixing operation is continued until the ammonia solution is uniformly distributed throughout the charge. The moist charge is then briquetted at a pressure of 3 tons per square inch and the briquettes dried in a drying oven for a period of 3 to 8 hours at a temperature of 120 C. The briquettes so produced have a density of 200 lbs. per cubic foot as compared with a bulk density of the molybdenum trioxide powder of 100 lbs. per cubic foot.

I claim:

1. A process for the production of rm coherent masses of a molybdenum oxide which comprises incorporating a small proportion of ammonium molybdate with molybdenum oxide in powdered form in the presence of water, pressing the mixture, and drying the pressed product.

2. A process for the production of rm coherent masses of a molybdenum oxide which comprises adding to the molybdenum oxide in powder form a proportion of an aqueous solution of arnmonia, pressing the mixture, and drying the pressed product.

3. A process as claimed in claim 1 in which the proportion of ammonium molybdate, calculated The mixed materials may then be 4 as a percentage of NH3 by weight on the weight of the molybdenum oxide, lies between 0.05% and 2%.

4. A process as claimed in claim 1 in which the proportion of water lies between .7% and 5% by Weight of the molybdenum oxide.

5. A process as claimed in claim 1 in which the pressing is conducted at a pressure lying between 2 and 20 tons per square inch.

6. A process as claimed in claim 1 in which the molybdenum oxide is molybdenum trioxide.

7. As a new article of manufacture, useful in the manufacture of alloys containing molybdenum, a rm coherent compacted mass of a composition consisting of molybdenum oxide containing a small proportion of ammonium molybdate intimately incorporated therewith as a binder.

8. As a new article of manufacture, useful in the manufacture of alloys containing molybdenum, a rm coherent compacted mass of a composition consisting of molybdenum oxide containing a small proportion of ammonium molybdate intimately incorporated therewith as a binder, said composition being substantially free from carbonaceous matter.

9. A process for the manufacture of alloys containing molybdenum which comprises adding to a molten metal bath containing a reducing agent in solution a firm coherent compacted mass of a composition consisting of molybdenum oxide containing a small proportion of ammonium molybdate intimately incorporated therewith as a binder.

l0. A process as defined in claim 9, in which said composition is substantially free from carbonaceous matter.

GEORGE LESLIE MILLER.

l REFERENCES CITED The following references are of record inthe le of this patent:

UNTED STATES PATENTS Number Name Date Re. 12,643 Ronay Apr. 30, 1907 900,587 Ramsey et al Oct. 6,1908 1,300,279 Kissock Apr. 15, 1919 5o 2,134,616 Linz Oct. 25, 1938 FOREIGN PATENTS Number Country Date 572,776 Great Britain Oct. 23, 1945 

